Electromotive Force Signal Research Articles

A Completely Configurable Digital System for Simultaneous Measurements of Hysteresis Loops and Barkhausen Noise

This paper describes a new accurate completely digital configurable computer-aided system for the simultaneous measurements of magnetic hysteresis loops and Barkhausen noise in a wide range of excitation frequencies (from 0.01 to 80 Hz) for the purposes of inspection of material properties and microstructure characterization. The importance of the correct choice of the data-acquisition (DAQ) card to have enough resolution in both hysteresis loop and magnetic Barkhausen noise (MBN) measurements is emphasized. Both the magnetic induction signal to construct the magnetic hysteresis loop and the Barkhausen noise are computed by the digital processing (numerical integration and digital filtering, respectively) of the induced electromotive force (EMF) signal. The accuracy of the hysteresis loop measurements is improved by using additional digital filters. The resolution of MBN results in simultaneous measurements is tested. Finally, some results of hysteresis loops and root-mean-square (RMS) envelopes of the MBN signal are presented to show the capability of the system to work at different excitation frequencies without changing any hardware.

Ground state magnetization distribution and characteristic width of head to head domain wall in Fe‐rich amorphous microwire

AbstractThe total magnetic charges of head to head domain walls, Q = 〈Mz〉 S, are measured for a family of amorphous glass‐coated Fe‐rich microwires by means of time integration of the electro‐motive force signals induced in a pick‐up coil wound around the wire. Here 〈Mz〉 is the average longitudinal wire magnetization and S is the cross‐section of the wire metallic core. The measured values of 〈Mz〉 = 1100–1200 emu/cm3 are close to the wire saturation magnetization. This means that Fe‐rich microwires of given family are nearly uniformly magnetized in its ground state, far from the wire ends. The characteristic width of the head to head domain wall is estimated to be δ ∼ (40–75) d, depending on the wall velocity, where d is the metallic core diameter. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Angular dependence of inverse spin–Hall effect induced by spin pumping investigated in aNi81Fe19/Ptthin film

The polar-angular dependence of the magnetization in electromotive force induced by the spin pumping has been investigated for a ${\text{Ni}}_{81}{\text{Fe}}_{19}/\text{Pt}$ film to examine the model of the inverse spin-Hall effect (ISHE). In the experiment, the magnetization-direction dependence of the electromotive force is estimated directly by the simultaneous measurement of the ferromagnetic resonance field and the electromotive force signal. The experimental results are well reproduced by a calculation based on the Landau-Lifshitz-Gilbert equation combined with the ISHE model.

PH-sensing properties of PbO2 thin film electrodeposited on carbon ceramic electrode

In this paper, a new highly sensitive potentiometric pH electrode is proposed based on the solid-state PbO2 film electrodeposited on carbon ceramic electrode (CCE). Two different crystal structures of PbO2, α and β were examined and the similar results were obtained. Moreover, the experimental results obtained for the proposed pH sensor and a conventional glass pH electrode were in good agreement. The electromotive force (emf) signal between the pH-sensitive PbO2-coated CCE and SCE reference electrode was linear over the pH range of 1.5–12.5. Near-Nernstian slopes of −64.82 and −57.85 mV/pH unit were obtained for α- and β-PbO2 electrodes, respectively. The interferences of some mono-valence and multi-valence ions on potentiometric response of the sensor were studied. The proposed pH sensor displayed high ion selectivity with respect to K+, Na+, Ca2+, and Li+, with log $$K_{H,M}^{{\text{pot}}} $$ values around −12 and has a working lifetime of about 30 days. Key parameters important for the pH sensor performance, including kind of PbO2 film, selectivity, response time, stability, and reproducibility, have been characterized. The proposed electrode showed a good efficiency for direct pH-metry after calibration and pH-metric titrations without calibration step. The response time was about 1 s in acidic medium and less than 30 s in alkaline solutions. The pH values of complex matrix samples such as fruit juices measured by the proposed sensor and a conventional glass pH electrode were in good agreement.

Investigation of numerical precision of 3-D RFECT signal simulations

This paper evaluates the numerical precision of a three-dimensional A/sub r/ method with edge-based finite elements in the simulation of remote field eddy-current testing of a ferromagnetic tube. The method is employed with a suitable formula for the electromotive force signal calculation in magnetic materials. Using a supercomputer, analyses of the mesh division effect on numerical precision are carried out to find out the proper mesh conditions for signal simulations of 3-D defects. Good agreements of the simulated signals with experimental ones are obtained using this method with an acceptable computational resource. In this way, the 3-D simulation of remote field eddy-current testing signals for a magnetic tube has become possible in practical applications.

Axial excited hybrid reluctant motor applied in electric vehicles and research of its axial coil signal

Characteristics of traction motors for electric vehicles (EV) should be high power density and high efficiency over the whole working area. The axial excited hybrid reluctant motor is fit for the EV application. In the motor, there are three excitation sources, which are permanent magnetic, armature, and axial coils. Controlling these excitation sources will make the motor run in different modes, which satisfy many kinds of conditions of the vehicle. With special structure and electromagnetic design, the electromagnetic torque includes reluctant torque, and the torque per unit volume is improved. Controlling the axial coil current will adjust the main flux. Then the flux weaken control is convenient achieved. When it is used as generator, main flux can be adjusted. The axial coil can also be used as position sensor. The electromotive force signal denoting the rotor position is added on the dc voltage applied on the axial coils. The paper introduces the structure and principle of the axial excited hybrid reluctant motor and resolves the electromagnetic torque. The axial magnetic field is analyzed. And the relation of the emf of the axial coils with the rotor position is produced. The simulation and experiment are made. The result shows that characteristics of this novel type motor satisfied the demands of the traction motor for EV.

Electrochemical Hydrogen Isotope Sensor Based on Solid Electrolytes

An electrochemical sensor of hydrogen isotopes based on solid electrolytes for determining the hydrogen isotope ratios and/or total hydrogen pressures in gases has been developed. This paper describes the methodology of the hydrogen isotope sensing together with experimental results. When hydrogen isotope gases are introduced to an electrochemical cell using a proton-conducting electrolyte (hydrogen isotope cell), the electromotive force (EMF) of the cell agrees with that theoretically estimated. The EMF signals can be used for the determination of the hydrogen isotope ratio in gases if the total hydrogen pressure is predetermined. By supplementary use of an oxide ion conductor cell, both the ratio and total pressure of the hydrogen isotopes can be simultaneously determined.

Solid-state pH nanoelectrode based on polyaniline thin film electrodeposited onto ion-beam etched carbon fiber

An ultramicro pH sensor has been constructed based on a thin polyaniline film that was electrochemically deposited onto a carbon fiber nanometer-size electrode. The substrate nanoelectrodes were fabricated using ion-beam conically etched carbon fibers with tip diameters ranging ca. from 100 to 500 nm. The polyaniline film was deposited from HCl solution containing the aniline monomer by cycling the potential between −0.2 and +1.0 V. The electromotive force (emf) signal between the pH sensitive polyaniline-coated nanoelectrode and an Ag/AgCl reference electrode was linear over the pH range of 2.0–12.5 with a slightly super-Nernstian slope of ca. −60 mV/pH unit. Response times ranged from several sec at pHs around 7 up to 2 min at pH 12.5. The proposed pH nanoelectrode displayed high ion selectivity with respect to K +, Na +, Ca 2+, and Li +, with log K H,M values around −12 and has a working lifetime of about 20 days. Key parameters important for the pH nanoelectrode performance, including polyaniline film preparation, selectivity, response time, temperature dependence, relative coating thickness, stability, and reproducibility, have been characterized and optimized. The performance of the pH nanoelectrode was examined by measuring the pH of several real samples including body fluids (serum, urine) and low ionic strength water samples (rain, deionized and tap water). The results agreed very well with those obtained by using commercial glass pH electrodes. The proposed pH nanoelectrode demonstrated attractive properties and seems particularly promising for use under physiological conditions.

NO x detection using the electrolysis of water vapour in a YSZ cell : Part I. NO x detection

The reaction of NO with the hydrogen formed by electrolyzing water vapour in a YSZ cell has been applied to detect NO with output signal of magnitude in millivolt or milliampere. The experimental apparatus consisted of two YSZ cells, Pt|YSZ|Pt, which served as an electrolysis cell and an oxygen sensor, respectively. A mixture of 0–3000 ppm NO and 3% H 2O in argon was successively fed to the two cells at 800°C. In the upstream cell, the hydrogen formed by electrolyzing water vapour in the sample gas reacted with NO in the sample gas. In the downstream cell, the electromotive force (EMF) value was measured using air as a reference gas. The EMF value of the oxygen sensor was used as a sensor signal, when a current of 6.7 mA was applied to the electrolysis cell. The EMF signal decreased with increasing NO concentration in the sample gas. Furthermore, the current applied to the electrolysis cell was used as another sensor signal, when the EMF value of the oxygen sensor was held at 700 mV. The current signal increased with increasing NO concentration in the sample gas.

Eddy current testing by upgraded microloop magnetic sensor array

AbstractA micro‐eddy current testing (ECT) probe, which consists of a planar microloop inductive magnetic sensor array and a pancake‐type exciting coil, was developed to upgrade the ECT technology, especially as it is used for inspecting steam generator tubing in a pressurized nuclear power plant (PWR). Eddy currents and resultant magnetic fields are perturbed due to a flaw in a conductor. The flaw is detected via perturbation of the electromotive force (EMF) and phase from the array. Flaws manufactured by electric discharge machining in INCONEL 600 planar specimens, the thickness of which was 1.25 mm, were detected and reconstructed by using stacked database and simplified algorithm. Even an outer‐edged 10 percent flaw could be detected. Measured EMF and phase signals were compared with numerical results obtained by using a three‐dimensional eddy current and field analysis code and then verified. The experiment confirmed that the spatial resolution of detection of the micro‐ECT probe is superior to that of the conventional pancake‐type ECT probe. Finally, it was demonstrated that it is possible to establish the same measurement speed using the micro‐ECT probe as it is by using the pancake‐type ECT probe.

Sensitivity of non-steady-state photoelectromotive force-based adaptive photodetectors and characterization techniques

The light-to-electricity conversion efficiency of the non-steady-state photoelectromotive force effect and its threshold sensitivity for the detection of phase-modulated optical signals and space-charge electric fields are evaluated. It is shown that for the optimal conditions of operation (the carrier spatial frequency is equal to the inverse diffusion length of the photocarriers, the detected frequency is higher than the cutoff frequency of the electromotive force signal, and the load resistance is higher than the resistance of the sample), the generation-recombination noise is approximately equal to the thermal noise of the sample resistance. In this case the threshold sensitivity of the adaptive photodetector without an external dc bias is independent of the parameters of the crystal used and can be only 4√2 times lower than that caused by the generation-recombination noise in a conventional photoresistor. Unlike in photodiodes and photoresistors, the output noise caused by laser intensity fluctuations is of the multiplicative type in the adaptive photodetectors.

Time-dependent effects in Faraday rotation in pulsed magnetic fields: an explanation

Published measurements of Faraday rotation in a variety of materials in pulsed magnetic fields show a time-dependent or hysteresis effect in which the angle of rotation lags the magnetic field as a function of time. We show that this effect is an artifact introduced by using a passive resistance-capacitance circuit to integrate the induced electromotive force (EMF) from a pickup coil to obtain the magnetic field. By numerically integrating the sampled-induced EMF signal, the effect vanishes. However, we propose an experimental situation where such a time lag should appear, allowing measurement of the spin-lattice relaxation time of the ion responsible for the Faraday rotation.

Magnetoflyer method for measuring gas-gun projectile velocities

The magnetoflyer method has been developed as a convenient and fiducial technique for measuring projectile velocities from propellent and gas guns. The velocity is estimated from the time interval between two electromotive force signals when the projectile, which includes a small ferrite magnet, passes through two pick-up coils. It was confirmed that the method was available up to 5 mm/μs.